Photoconductive waveform memory

ABSTRACT

A photoconductive waveform memory having a plurality of photoelectric converters receptive of a light pattern representative of a memorized waveform. Each photoelectric converter comprises an elongated resistance element comprising a plurality of resistive pieces connected in series with a plurality of electrically conductive layers; an elongated conductive element in parallel with the resistive element; and a photoconductive strip between and in continuous contact with the elongated resistive and conductive elements.

[11] 3,885,151 1 May 20, 1975 United States Patent 1 Tokushima 340/173 LS 250/211 J 250/209 317/235 N 250/2ll J 146/74 P 1; am W nc mumo m flufimmm .Ma heo SHMCGT 790 2 6 0777% M99999 wwuuwo 257525 73279 786796 40 80 3 333333 PHOTOCONDUCTIVE WAVEFORM MEMORY [75] Inventor: Tadao Tokushima,Hamamatsu,

Japan ry having a plueptive of a light rized waveform. rises an elongated urality of resistive plurality of electrie element; and a phontact RV [)n I 2 m A A/ Robert E. Burns;

; an elongated conductive ele- Bruce L. Adams ABSTRACT Rn Qn 5 Claims, 3 Drawing Figures Primary Examiner.lames W. Lawrence Assistant ExaminerD. C. Nelms Attorney, Agent, or Firm Emmanuel J. Lobato A photoconductive waveform memo rality of photoelectric converters rec pattern representative of a memo Each photoelectric converter comp resistance element comprising a pl pieces connected in series with a cally conductive layers ment in parallel with the resistiv toconductive strip between and in continuous co with the elongated resistive and conductive elements.

HOlj 39/12 250/211 R, 211 K, 211.1, 578; 340/343 P, 146.3 Z,

LT; 346/74 P; 317/235 N W/AQA/A PATENIEB MAY 20 I975 SHEET 2 [IF 2 PHOTOCONDUCTIVE WAVEFORM MEMORY BACKGROUND OF THE INVENTION This invention relates to a waveform memorizing device which affords memorization, as sampled values, of the waveforms of various tones or sounds to be created in an electronic musical instrument, or envelopes and the like of the tones or sounds.

In an electronic musical instrument, it is frequently required to measure or specify waveforms or envelopes of the tones or sounds created therein. This invention is directed toward satisfying such a demand and to provide a waveform memorizing device wherein the waveforms or envelopes can be memorized and read out with ample precision.

SUMMARY OF THE INVENTION According to the present invention, there is provided, in a waveform memorizing device comprising means for forming a light pattern indicative of a waveform to be memorized in an optical manner, and a photoelectric converter which is arranged in opposition to the light-p attern forming means and includes a plurality of photoelectric potentiometers exhibiting respective sampled values constituting a waveform defined by the light pattern and disposed in parallel with each other and in a direction facing toward a time axis of the waveform to be memorized in the waveform memorizing device, an improvement wherein each of the photoelectric potentiometers comprises: a band-like resistor element, which is in itself a combination of a plurality of resistance pieces arranged along the length of the resistor element with electrically conductive layers interposed therebetween; a band-like electrically conductive element disposed in parallel with the band-like resistor element; and a narrow band of a photoconductive substance interposed between the two elements for bridging the same elements when a part of the substance is exposed to light.

The band-like resistor element of each photoelectric potentiometer is, according to the present invention, further divided into a plurality of resistance pieces instead of it being made of a single piece of resistance body, whereby any variation in irradiated position on the photoconductive substance can be read out from the band-like electrically conductive element in the form a voltage variable in a digital manner. More specifically, although the detection of any minute variation in the irradiated position along the resistance element made of a single piece of resistance body is difficult because of the characteristic deviation caused during the production of the resistance element, such a variation of the irradiated position can be easily detected when in resistance element is divided into a plurality of resistance pieces as described above, and the precision of the results thus read out can be thereby improved.

The nature and further features of invention will now be more fully apparent by the following detailed description with respect to a preferred embodiment thereof with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. I is a plan view of a waveform memorizing device for an electronic musical instrument constituting an embodiment of the present invention;

FIG. 2 is a circuit diagram for a waveform read out circuit (illustrated schematically) in which is included the waveform memorizing device in the form of an equivalent circuit; and

FIG. 3 is a graph indicating an output characteristic of a photoelectric potentiometer which constitutes an essential component of the waveform memorizing device according to the present invention.

DETAILED DESCRIPTION As illustrated in FIG. 1, the waveform memorizing device according to the present invention, which is adapted for memorizing waveforms defining various tone colors created in an electronic musical instrument, comprises means 3 for forming a light pattern indicative of a waveform to be memorized in an optical manner, and a photoelectric converter 2 which is arranged integrally with the light-pattern forming means 3 at a position opposed to the latter. The light-pattern forming means 3 may include a pair of light shielding members B, and 8,, so that a gap A formed between the members represents a waveform to be memorized. The photoelectric converter 2 receiving the image of the light pattern comprises an insulating substrate 1, on which a plurality of photoelectric potentiometers P, through P,, are formed in a mutually parallel disposition in a direction perpendicular to the time axis along which the light pattern is displayed.

Each of the photoelectric potentiometers P, through P,, comprises a band-like resistor element R,, a bandlike electrically conductive element D, made of P,, I,,, or the like, which is disposed in parallel with the resistor element R,, and a narrow band of a photoconductive substance C,, such as CdS, which is interposed between the two elements R, and D, for bridging the same elements.

According to the present invention, the band-like resistance element R, is made up of a plurality of resistance pieces r, through r, made of, for instance, a Ni-Cr alloy and arranged along the length of the resistance element R,. The resistance pieces r, through r, are connected in series, with electrically conductive layers m, through m interposed alternately between adjacent resistance pieces.

The ends of the band-like resistance elements R, through R, at one side thereof are commonly connected to a conductive strip O, which is further connected to a terminal T while the ends of the resistance elements R, through R, at the other side thereof are connected commonly to another conductive strip 0,, which is in turn connected to a terminal T,,. The ends of the electrically conductive elements D, through D,, are connected, at one side thereof, with terminals T, through T,,, respectively.

An electric circuit for reading out a waveform memorized in the memorizing device is indicated in FIG. 2 in which the above described photoelectric converter is indicated in the form of an equivalent circuit. The read out circuit operates as follows.

When a power source voltage E is connected between the terminals T,, and T,,, a voltage E obtained from the terminal T, of, for instance, a first potentiometer P, is varied in a stepwise manner as shown in FIG. 3 in response to the variation in the irradiated position I measured along the length of the resistance element R, of the potentiometer P,. The voltages obtained from the terminals T, through T, of the potentiometers P,

through P, are varied in the same manner as in the first potentiometer P Thus, when the parallel potentiometers P, through P, are irradiated by a light pattern representing a wave form as shown in FIG. 1, this means that the irradiated positions (of low resistance) on the photoconductive layers C through C each of the positions corresponding to a sliding contact point along a potentiometer shown in FIG. 2 in an equivalent circuit, are determined by the irradiated light pattern. The potentiometers P through I, thus deliver from their output terminals T through T output voltages each correspond ing to a fraction of the power source voltage E determined by the position of the sliding contact along the corresponding potentiometer. When the output voltages from the terminals T through T,, are successively read out by a transfer means H having an output terminal T a sampled voltage-waveform analogous to the waveform represented by the light pattern can be read out with precision from the output terminal T In the above described construction of band-like resistance elements R through R if the number of the resistance pieces r through r included in each of the resistance elements is increased, the accuracy of the voltage-waveforms read out from the output terminal T can be substantially improved.

What we claim is:

l. In a waveform memory which comprises. in combination;

a. means for forming a light pattern representative of a memorized waveform, said light pattern having an extent in a first direction representative of time and having an extent in a second direction representative of the amplitude of the memorized waveform at each value of time represented along said first direction; and

b. a photoelectric converter comprising a substrate for receiving the image of the waveform on a surface of the substrate and a plurality of elongated photoelectric potentiometers arranged in parrallel on the surface of the substrate and extending in said second direction, whereby an electric signal developed by each of said photoelectric potentiometers corresponds to a value of the waveform at a discrete point along the first direction representative of time,

the improvement wherein each of said photoelectric potentiometers comprises:

1. an elongated resistance element comprising a plurality of resistive pieces connected in series, and a plurality of electrically conductive layers interposed alternately therebetween;

2. an elongated electrically conductive element disposed in parallel with said elongated resistance element; and

3. a strip of photoconductive substance interposed between said resistance element and said conductive element and continuously contacting said resistance and said conductive elements along their respective lengths.

2. A waveform memory as set forth in claim 1 wherein said plurality of resistive pieces includes in said elongated resistance element are made of a Ni Cr alloy.

3. A waveform memory as set forth in claim 1 wherein said elongated electrically conductive element is made of a corrosion-resistance metal selected from the group consisting of P, and I,,.

4. A waveform memory as set forth in claim 1 wherein the strip of a photoconductive substance interposed between the resistance element and the electrically conductive element is C 5.

5. A waveform memory as set forth in claim 1 further comprising, a voltage source and means electrically connecting the ends of said resistance elements across said voltage source. 

1. In a waveform memory which comprises, in combination; a. means for forming a light pattern representative of a memorized waveform, said light pattern having an extent in a first direction representative of time and having an extent in a second direction representative of the amplitude of the memorized waveform at each value of time represented along said first direction; and b. a photoelectric converter comprising a substrate for receiving the image of the waveform on a surface of the substrate and a plurality of elongated photoelectric potentiometers arranged in parrallel on the surface of the substrate and extending in said second direction, whereby an electric signal developed by each of said photoelectric potentiometers corresponds to a value of the waveform at a discrete point along the first direction representative of time, the improvement wherein each of said photoelectric potentiometers comprises:
 1. an elongated resistance element comprising a plurality of resistive pieces connected in series, and a plurality of electrically conductive layers interposed alternately therebetween;
 2. an elongated electrically conductive element disposed in parallel with said elongated resistance element; and
 3. a strip of photoconductive substance interposed between said resistance element and said conductive element and continuously contacting said resistance and said conductive elements along their respective lengths.
 2. an elongated electrically conductive element disposed in parallel with said elongated resistance element; and
 2. A waveform memory as set forth in claim 1 wherein said plurality of resistive pieces includes in said elongated resistance element are made of a Ni - Cr alloy.
 3. A waveform memory as set forth in claim 1 wherein said elongated electrically conductive element is made of a corrosion-resistance metal selected from the group consisting of Pt and In.
 3. a strip of photoconductive substance interposed between said resistance element and said conductive element and continuously contacting said resistance and said conductive elements along their respective lengths.
 4. A waveform memory as set forth in claim 1 wherein the strip of a photoconductive substance interposed between the resistance element and the electrically conductive element is CdS.
 5. A waveform memory as set forth in claim 1 further comprising, a voltage source and means electrically connecting the ends of said resistance elements across said voltage source. 